This invention relates generally to manufacturing processes for constructing injection nozzles. More particularly, this invention relates to processes for manufacturing elongated nozzle body tips of fuel injectors such as may be employed in internal combustion engines.
In fuel injection nozzles of the valve closing orifice type to which the present invention has particular applicability, the nozzle body has an elongated narrow form which terminates in an elongated tip having a reduced diameter. The tip is a separate component which is inserted into the end of the nozzle body. A shouldered compression ring seals between the tip and the nozzle body to seal and insulate the nozzle body from combustion pressure, hot combustion gases, and combustion products. An elongated reciprocating valve is disposed in the nozzle body. The valve includes a valve surface which seals against a conical seat formed at the interior end of the tip. Injection spray orifices are formed in the nozzle tip to provide fluid communication from the nozzle for injection of fuel or other applications.
Because of the elongated characteristics of the valve and the pressures exerted on the valve, an integral collar defining a cylindrical lower guide surface may be formed at the nozzle tip interior to prevent bowing of the valve and eccentric valve operation. The lower guide surface must be finished within precise tolerances in order to achieve proper valve operation. Because the nozzle tip guide surface has an inside diameter which is less than the inside diameter of the nozzle tip bore for most of the longitudinal extent of the nozzle tip body, manufacturing the internal guide surface can be problematical and costly.
Lower guide surfaces are also advantageous in pintle-type injectors which employ an elongated axially displaceable valve. The injection opening of the nozzle opens generally axially through the end of the nozzle body.
In conventional manufacturing processes to which the invention relates, a nozzle tip blank is initially formed from cold rolled steel. The internal conical seat, the valve tip bore and the lower guide surface are precisely ground to form the finished surfaces. The nozzle tip has enlarged bore portions disposed between the guide surface and the valve seat formed at the interior distal tip as well as enlarged bore portions disposed between the proximal end of the nozzle tip and the guide surface. Consequently, the grinding and finishing steps of the nozzle tip body requires precise longitudinal and radial positioning of the guide surface and precise dimensioning of the guide surface.